Piston cooling jet for an internal combustion engine

ABSTRACT

A piston cooling jet for an internal combustion engine includes a body having a coolant duct extending between a coolant duct inlet and a coolant duct outlet fluidly connected to a coolant nozzle. The piston cooling jet includes a plunger having a plunger stem and a plunger head. The plunger is movable within the coolant duct of the body between a closing position that closes the coolant duct inlet and an opening position that opens the coolant duct inlet. The piston cooling jet further includes a biasing spring coupled to the plunger to bias it towards the closing position. A plunger coolant channel has an inlet at the plunger head and an outlet at the plunger stem, channeling coolant downstream of the plunger head when the plunger is in the opening position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Great Britain Patent Application No.1519640.5, filed Nov. 6, 2015, which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present disclosure pertains to the cooling of the pistons of aninternal combustion engine, and more particularly to piston cooling jetsfor an internal combustion engine.

BACKGROUND

An internal combustion engine (ICE) generally includes an engine blockdefining one or more cylinders, each provided with a reciprocatingpiston coupled to a crankshaft. A cylinder head closes the cylinders todefine a combustion chamber for each cylinder, where injection andignition of a fuel and air mixture cyclically occurs, causing the abovementioned reciprocating movement of the piston.

In order to improve the internal combustion engine performances, pistonsare preferably cooled. Devices known as piston cooling jets (PCJs) areused to generate jets of oil onto the underside of the pistons. The oilmay be used to absorb heat from the pistons and also to lubricate thecylinders of the internal combustion engine.

Piston cooling jets include a coolant inlet, which is typically openedand closed by a movable plunger reciprocating within the piston coolingjet. The piston cooling jet further includes a nozzle to direct thecoolant towards the underside of the pistons in the cylinder of theengine block. The plunger is biased by a spring towards the coolantinlet, to close it. When a force generated by the coolant exceeds thebiasing force of the spring, the plunger is moved away from the coolantinlet, so that coolant can flow within the piston cooling jet. Thespring and the plunger are supported by a carrier within the pistoncooling jet. When the coolant inlet is opened, the coolant flowslaterally with respect to the carrier, so as to avoid contact betweenthe coolant and the spring that may cause undesired turbulence withinthe coolant itself. Also, the carrier is designed and arranged withinthe piston cooling jets, so as to limit the maximum stroke of theplunger.

As a result, the coolant flow requirements are respected and alsocoolant consumption is limited. Moreover, the carrier acts as a strokelimiter to maintain the flow of coolant as constant as possible when thecoolant pressure continues to be raised.

Furthermore, a balance between the performance improvements and thepower required to operate the piston cooling jets and the fuelconsumption (and consequently CO₂ emission) is achieved. In particular,the flow of coolant (viewed as a function of the coolant pressure) has astep-like behavior, which provides for an effective operation of thepiston cooling jet.

However, the carrier is a relatively complex component. Also it isparticularly difficult and complex to insert the carrier within thepiston cooling jets. As a result, the piston cooling jets require acertain number of elements that are complex and timely to assemble, thusreducing the cost effectiveness of the piston cooling jet.

Accordingly, there is a need to provide a piston cooling jet composed ofa reduced number of components that is simple to produce and to assemblein a cost-effective manner.

SUMMARY

According to an embodiment, a piston cooling jet for an internalcombustion engine includes a body having a coolant duct extendingbetween a coolant duct inlet and a coolant duct outlet that is fluidlyconnected to a coolant nozzle. The piston cooling jet includes a plungerprovided with a plunger stem and with a plunger head. The plunger ismovable within the coolant duct of the body between at least a closingposition wherein the plunger head closes the coolant duct inlet and anopening position. The plunger head is at a distance from the coolantduct inlet to open the coolant duct inlet. The piston cooling jetfurther includes a biasing spring arranged within the coolant duct andcoupled to the plunger to bias it towards the closing position. Theplunger is provided with at least one plunger coolant channel having achannel inlet on the plunger head and a channel outlet on the plungerstem, channeling coolant downstream of the plunger head when the plungeris in the opening position.

As a result, the above mentioned step-like behavior of the flow ofcoolant can be achieved with a reduced number of simple components.Hence, the above mentioned advantages mentioned for the known complexpiston cooling jets are achieved in a simpler and inexpensive manner.

According to an embodiment, at least part of the plunger coolant channelis a recess provided on the plunger stem and/or on the plunger head. Inother words the plunger stem and/or the plunger head is provided with atleast one recess defining at least part of the plunger coolant channel.This is a simple and effective manner to realize the above mentionedplunger coolant channel(s).

According to an embodiment, the plunger stem and/or the plunger head hasa cross section substantially cross-shaped. In other words, at leastpart of the plunger coolant channel(s) is/are defined on the externalsurface of the plunger, and are parallel with respect to a longitudinalaxis of the body. These particular shapes have proven to be particularlyeffective.

According to an embodiment, at least part of the plunger coolant channelis a duct provided within said plunger stem and/or said plunger head. Inother words, the plunger stem and/or the plunger head is provided withat least one duct defining at least part of the plunger coolant channel.Therefore, at least part of the plunger coolant channel(s) is obtainedby a duct passing inside the plunger. This allows an improved guidanceof the coolant.

According to an embodiment, the biasing spring is a helical coil springcoupled to at least a portion of the lateral surface of the plungersteam and at least part of the plunger coolant channel is extendingwithin the inner hollow space of the coil spring. By doing so, thecoolant is channeled by the plunger coolant channel inside the innerhollow space of the spring thus avoiding undesired turbulence effects.In fact, the fluid is not directed towards the spring, which may causeturbulence in the flow of coolant.

According to an embodiment, the plunger is provided with a plurality ofplunger coolant channels, preferably arranged symmetrically with respectto a plunger longitudinal axis. This allows managing an increased flowof coolant. Also, it is simpler to make the system symmetric, so as toobtain a more regular flow of coolant.

According to an embodiment, a portion of the plunger coolant channel atthe plunger head is arranged substantially perpendicular, or inclined,with respect to a plunger longitudinal axis. According to an embodiment,a portion of the plunger coolant channel at the plunger head is arrangedsubstantially radially with respect to a plunger longitudinal axis. As aresult, a good guidance of the flow of coolant is obtained.

According to an embodiment, a portion of the plunger coolant channel atthe plunger stem is arranged substantially parallel with respect to thelongitudinal axis. This allows obtaining a regular flow of fluid.Moreover, the fluid is not directed towards the spring, which may causeturbulence in the flow of coolant.

According to an embodiment, the plunger head is dimensioned so that, inthe opening position, the plunger is distanced from the coolant ductinlet by a distance that is less than the height of the plunger head. Inother words, the maximum stroke of the plunger is smaller than theheight of the plunger head. As a result, the plunger reaches theabutting portion in short time (i.e. the plunger can switch between theclosing position and the opening position in a short time). Also, in theopening position the space between the plunger head and the coolant ductinlet is filled in short time, so that the above mentioned step-likebehavior of the flow of coolant can be achieved.

According to an embodiment, the coolant duct is provided with a plungerabutting portion that is contacted by the plunger head in the openingposition of the plunger. Advantageously by providing the abuttingportion for the plunger head on the coolant duct, and preferably on aninner surface of the coolant duct, it is possible to reduce the numberof components of the piston cooling jet.

A further embodiment of the present disclosure provides for an internalcombustion engine including a piston cooling jet according to one ormore of the preceding aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements.

FIG. 1 shows an exemplary embodiment of an automotive system includingan internal combustion engine in which the fuel unit pump can be used;

FIG. 2 is a cross-section according to the plane A-A of an internalcombustion engine belonging to the automotive system of FIG. 1;

FIG. 3 is a perspective view of a piston cooling jet according to anembodiment of the present disclosure;

FIG. 4 is a front sectional view of the piston cooling jet of FIG. 3,with the plunger in the closing position;

FIG. 5 is a view similar to FIG. 4, with the plunger in the openingposition;

FIG. 5 is a bottom view of a plunger according to an embodiment of thepresent disclosure;

FIG. 7 is a perspective view of the plunger of FIG. 6;

FIG. 8 is schematic view of a desired and ideal behavior of the flow ofcoolant in a piston cooling jet; and

FIG. 9 is a schematic view of the actual behavior of the flow of coolantin a piston cooling jet according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by any theorypresented in the preceding background of the invention or the followingdetailed description.

Some embodiments may include an automotive system 100, as shown in FIGS.1 and 2, that includes an internal combustion engine (ICE) 110 having anengine block 120 defining at least one cylinder 125 having a piston 140coupled to rotate a crankshaft 145. A cylinder head 130 cooperates withthe piston 140 to define a combustion chamber 150. A fuel and airmixture (not shown) is disposed in the combustion chamber 150 andignited, resulting in hot expanding exhaust gasses causing reciprocalmovement of the piston 140. The fuel is provided by at least one fuelinjector 160 and the air through at least one intake port 210. The fuelis provided at high pressure to the fuel injector 160 from a fuel rail170 in fluid communication with a high pressure fuel pump 180 thatincrease the pressure of the fuel received from a fuel source 190.

Each of the cylinders 125 has at least two valves 215, actuated by thecamshaft 135 rotating in time with the crankshaft 145. The valves 215selectively allow air into the combustion chamber 150 from the port 210and alternately allow exhaust gases to exit through a port 220. In someexamples, a cam phaser 155 may selectively vary the timing between thecamshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through anintake manifold 200. An air intake duct 205 may provide air from theambient environment to the intake manifold 200. In other embodiments, athrottle body 330 may be provided to regulate the flow of air into themanifold 200. In still other embodiments, a forced air system such as aturbocharger 230, having a compressor 240 rotationally coupled to aturbine 250, may be provided. Rotation of the compressor 240 increasesthe pressure and temperature of the air in the duct 205 and manifold200. An intercooler 260 disposed in the duct 205 may reduce thetemperature of the air. The turbine 250 rotates by receiving exhaustgases from an exhaust manifold 225 that directs exhaust gases from theexhaust ports 220 and through a series of vanes prior to expansionthrough the turbine 250. The exhaust gases exit the turbine 250 and aredirected into an exhaust system 270. This example shows a variablegeometry turbine (VGT) with a VGT actuator 290 arranged to move thevanes to alter the flow of the exhaust gases through the turbine 250. Inother embodiments, the turbocharger 230 may be fixed geometry and/orinclude a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one ormore exhaust aftertreatment devices 280. The aftertreatment devices maybe any device configured to change the composition of the exhaust gases.Some examples of aftertreatment devices 280 include, but are not limitedto, catalytic converters (two and three way), oxidation catalysts, leanNOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR)systems, and particulate filters. Other embodiments may include anexhaust gas recirculation (EGR) system 300 coupled between the exhaustmanifold 225 and the intake manifold 200. The EGR system 300 may includean EGR cooler 310 to reduce the temperature of the exhaust gases in theEGR system 300. An EGR valve 320 regulates a flow of exhaust gases inthe EGR system 300.

The automotive system 100 may further include an electronic control unit(ECU) 450 in communication with one or more sensors and/or devicesassociated with the ICE 110. The ECU 450 may receive input signals fromvarious sensors configured to generate the signals in proportion tovarious physical parameters associated with the ICE 110. The sensorsinclude, but are not limited to, a mass airflow and temperature sensor340, a manifold pressure and temperature sensor 350, a combustionpressure sensor 360, coolant and oil temperature and level sensors 380,a fuel rail pressure sensor 400, a cam position sensor 410, a crankposition sensor 420, exhaust pressure and temperature sensors 430, anEGR temperature sensor 440, and an accelerator pedal position sensor445. Furthermore, the ECU 450 may generate output signals to variouscontrol devices that are arranged to control the operation of the ICE110, including, but not limited to, the fuel unit pump 180, fuelinjectors 160, the throttle body 330, the EGR Valve 320, the VGTactuator 290, and the cam phaser 155. Note, dashed lines are used toindicate communication between the ECU 450 and the various sensors anddevices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital centralprocessing unit (CPU) in communication with a memory system 460, or datacarrier, and an interface bus. The CPU is configured to executeinstructions stored as a program in the memory system, and send andreceive signals to/from the interface bus. The memory system 460 mayinclude various storage types including optical storage, magneticstorage, solid state storage, and other non-volatile memory. Theinterface bus may be configured to send, receive, and modulate analogand/or digital signals to/from the various sensors and control devices.

Instead of an ECU 450, the automotive system 100 may have a differenttype of processor to provide the electronic logic, e.g. an embeddedcontroller, an onboard computer, or any processing module that might bedeployed in the vehicle.

With reference to FIGS. 3-7, a piston cooling jet 1 includes a body 2and a nozzle 3. The body 2 includes a coolant duct 20 having a coolantduct inlet 21 and a coolant duct outlet 22 fluidly connected to thenozzle 3. A plunger 4 is movable in a reciprocating manner within thecoolant duct 20 and is provided with a plunger longitudinal axis A.

The body 2 typically has an elongated shape, and is provided with alongitudinal axis that is parallel or coincident to the plungerlongitudinal axis A (In the following reference will be made to theplunger longitudinal axis A). Generally, the body 2 is substantiallycylindrical. The nozzle 3 is configured in a known manner to directcoolant 5 towards a piston 140 in operative condition. It should benoted the coolant is schematically show in FIG. 5 by arrows 5schematically showing its flow path.

The coolant duct 20 passes through the body 2. Typically, at least partof the coolant duct 20 is extending substantially axially with respectto the plunger longitudinal axis A. In an embodiment, the coolant ductinlet 21 is placed at one end of the body 2, and allows inlet of coolant5 along a direction substantially parallel with respect to the plungerlongitudinal axis A. In the shown embodiment, the coolant duct 20 isprovided with two coolant outlets 22. The coolant outlets 22 areoriented radially with respect to the plunger longitudinal axis A.

A coolant collector 6 is partially disposed around the body 2 to collectthe coolant 5 exiting from the body and to direct it towards the nozzle3. In particular, a pipe 7 carrying the nozzle 3 is coupled to thecoolant collector 6.

The coolant duct 20 is further provided with a plunger abutting portion23, configured to engage the plunger 4 (in particular the plunger head 4a of the plunger 4, better discussed below). Typically, the plungerabutting portion 23 is obtained by converging portion (considering thedirection of flow of the coolant 5) of the coolant duct 20. In general,at the plunger abutting portion 23, the diameter of the cooling duct 20is smaller than the maximum width of the plunger, so that movement ofthe plunger 4 is stopped by the plunger abutting portion 23, when theplunger 4 moves away from the coolant duct inlet 21. In general, thenumber and disposition of the coolant ducts inlet and outlet may varywith respect to what shown. Moreover, in other embodiments, the coolantcollector 6 may be absent, e.g. a pipe 7 may be directly connected to acoolant duct outlet 22.

The plunger 4 is provided with a plunger head 4 a and with a plungerstem 4 b. Typically, the plunger head 4 a has a greater width (and ingeneral greater cross section) and a smaller height with respect to thewidth and the height of the plunger stem 4 b. The plunger 4 is movablewithin the coolant duct 20 of the body 2 between at least a closingposition (shown in FIG. 4) wherein the plunger head 4 a closes thecoolant duct inlet and an opening position (shown in FIG. 5) wherein theplunger head 4 a reaches a plunger abutting portion 23 of the coolantduct 20, at a distance D from the coolant duct inlet 21.

According to an embodiment, the plunger head 4 a is dimensioned so that,in the opening position, the plunger is distanced from the coolant ductinlet 21 by a distance D that is less than the height H of the plungerhead 4 a. As a result, the maximum stroke of the plunger 4 within thecoolant duct 20 is short. In an embodiment, the plunger 4 reciprocatesalong a direction that coincides with (or at least is parallel withrespect to) the plunger longitudinal axis A.

A biasing spring 8 is inserted within the coolant duct 20. Inparticular, biasing spring 8 is arranged within the coolant duct 20 soas to bias the plunger 4 in the closing position, i.e. towards thecoolant duct inlet 21. As mentioned, in the closing position, theplunger 4, and in particular the plunger head 4 a, contacts the coolinginlet 21 so as to close it. In other words, in the closing position,fluid tight engagement is obtained between the cooling inlet 21 and theplunger 4, in order to prevent coolant from entering within the body 2.Gaskets or other sealing members may be used at the cooling inlet 21 tohelp in providing the above mentioned fluid tight engagement.

According to an embodiment, the biasing spring 8 is typicallydimensioned so that its external diameter substantially coincides withthe diameter of the portion of the coolant duct 20 into which it isinserted, while the inner diameter of the biasing spring 8 substantiallycoincides with the maximum width of the plunger stem 4 b. According toan embodiment, the plunger 4 is partially inserted within the biasingspring 8 so that the biasing spring 8 exerts its biasing force againstthe plunger head 4 a. The external surface (or part of the externalsurface, as better discussed later) of the plunger stem 4 b contacts thebiasing spring 8, so that tilting of the plunger 4 with respect to thebiasing spring 8 is prevented.

The plunger 4 is provided with at least one plunger coolant channel 41,42 allowing flow of coolant 5 within the coolant duct 20 downstream theplunger head 4 a (considering the direction of flow of coolant 5, i.e.from the coolant duct inlet 21 towards the coolant duct outlet 22) whenthe plunger 4 is in the opening position. In particular, the plungercoolant channel(s) 41, 42 is/are provided with a channel inlet 41 a, 42a and with a channel outlet 41 b, 42 b. The channel inlet 41 a, 42 a isarranged on the plunger head 4 a, while the channel outlet 41 b, 42 b isarranged on the plunger stem 4 b.

According to an embodiment, the channel inlet 41 a, 42 a is arranged sothat the coolant 5 flows in the plunger coolant channel 41, 42 into thechannel inlet 41 a, 42 a in a radial direction with respect to theplunger longitudinal axis A. The channel outlet 41 b, 42 b is arrangedso that the coolant 5 leaves the plunger coolant channel 41, 42substantially along a direction parallel with respect to the plungerlongitudinal axis A.

The plunger coolant channel(s) 41, 42 may be arranged according tovarious configurations. In FIGS. 4 and 5 two possible embodiments areshown. In particular, a plunger coolant channel 41 (shown on the leftportion of the plunger 4) may be obtained as a recess, e.g. a missing orcut-away portion on the external surface of the plunger 4. In anotherembodiment, a plunger coolant channel 42 (shown on the right portion ofthe plunger 4) may be obtained as a duct (or hole) within the plunger 4.Plunger coolant channel 41 configured as a recess allows the coolant toflow along the external surface of the plunger 4, while plunger coolantchannel 42 configured as a duct allows the coolant to flow within theplunger 4.

In FIGS. 4 and 5, it is shown an embodiment where a plunger 4 isprovided with two different kinds of plunger coolant channels 41, 42(i.e. the two above discussed), but generally a single embodiment isprovided with only one kind of plunger coolant channels. In FIGS. 6 and7 an embodiment is shown wherein a plunger 4 is provided with fourplunger coolant channels 41, configured as recesses on the externalsurface of the plunger 4. The plunger coolant channels 41 are evenlydistributed along the external surface of the plunger 4, so that theplunger 4 is provided with two planes of symmetry, substantiallyorthogonal one to the other.

In more detail, the plunger head 4 a is provided with a first portion 40a substantially cylindrical, acting as a shutter for the coolant ductinlet 21, and a second portion 40 b provided with recesses to define theplunger coolant channels 41. The second portion 40 b, viewed in crosssection, is substantially cross shaped. The plunger stem 4 b is alsoprovided with recesses to define plunger coolant channels 41. As before,the cross section of the plunger stem 4 b is substantially cross-shaped.Other embodiments (not shown) may be provided with different shapedand/or with a different number of recesses to define coolant channels41.

In general, the plunger head 4 a may be provided with recesses (ormissing or cut-away portions) to define part of one or more channels 41so that, at the recesses, flow of coolant 5 between the plunger 4 andthe coolant duct 20 is allowed (typically along a directionsubstantially radial (or perpendicular) with respect to the plungerlongitudinal axis A). The remaining lateral surface of the plunger head4 a allows engagement with the plunger abutting portion 23. The plungerstem 4 b may be provided with recesses to define the remaining part ofthe channel(s) 41 so that, at the recess(es), flow of coolant 5 isallowed between the plunger 4 and the biasing spring 8 (typically alonga direction substantially parallel with respect to the plungerlongitudinal axis A). The remaining portion of the lateral surface ofthe plunger stem 4 b contacts the biasing spring 8.

More in detail, according to a possible embodiment, the biasing spring 8is a helical coil spring coupled to at least a portion of the lateralsurface of the plunger steam 4 b and at least part of the plungercoolant channel 41, 42 is extending within the inner hollow space S ofthe coil spring. More in detail, the channel outlet 41 b, 42 b isprovided within the inner hollow space of the spring.

According to an embodiment, considering a cross section of the plunger 4each of the plunger coolant channels 41 has an angular extension a ofabout 70 degrees. The maximum depth MD of the channel 41 is about ⅔ themaximum width of the plunger stem 4 b (i.e. the diameter of the plungerstem 4 b). This provides a good balance between allowing a sufficientflow of coolant and allowing an effective engagement between the plungerhead 4 a and the plunger abutting portion 23.

As mentioned, in other embodiments, plunger coolant channels 42 may beconfigured as ducts within the plunger 4. At the plunger head 4 a, theduct is preferably arranged substantially radially with respect to thelongitudinal axis A, while at the plunger stem 4 b the duct ispreferably arranged substantially parallel to the plunger longitudinalaxis. Different configurations, shapes and numbers of plunger coolantchannels 42 may be used allowing flow of coolant downstream the plungerhead 4 a when the plunger 4 is in the opening position. In general,typically plunger coolant channels 42 allow inlet of coolant 5 withinthe plunger head 4 a of the plunger 4, and outflow of coolant 5 from theplunger stem 4 b of the plunger 4.

In different embodiments, a plunger coolant channel may be configured inpart as a recess and in part as a duct. As an example, the portion ofchannels 41 shown in the figures may continue as a through duct withinthe plunger head 4 a.

As mentioned, in general a plunger coolant channel according to anembodiment of the present disclosure allows flow of coolant downstreamthe plunger head 4 a, i.e. it allows flow of coolant from upstream theplunger abutting portion 23 to downstream the plunger abutting portion23. In other words, a plunger coolant channel according to an embodimentof the present disclosure allows the coolant to bypass the engagementbetween the plunger 4 and the plunger abutting portion 23.

During assembly, the piston cooling jet 1 is inserted into a coolantcircuit of an automotive system 100, so that the coolant circuitprovides coolant 5 at the coolant inlet duct 21. The piston cooling jetis arranged in the automotive system so that the nozzle can direct aflow of coolant 5 towards the underside of a piston 140 in the engineblock 120 of the internal combustion engine 110 of the automotive system100.

During operation, the plunger 4 is initially in the closing position,shown in FIG. 4, biased by the biasing spring 8. The plunger head 4 acloses the coolant duct inlet 21, so that no coolant 5 is introducedinto the coolant duct 20. This is shown in the graph of FIG. 9. When thepressure of the coolant 5 in the coolant circuit is below value P1 (i.e.the value needed to move the plunger 4 away from the coolant duct inlet21), there is no flow of coolant 5.

When the pressure of coolant 5 in the coolant circuit exceeds thebiasing force of the biasing spring 8, the plunger 4 is moved away fromthe coolant duct inlet 21. In this situation, the flow of coolant 5 israpidly increased, until the space between the plunger 4 and the coolantduct inlet 21 is filled. In the graph of FIG. 9, this is shown by therapid increase in the flow of coolant for values of pressure above valueP1. Subsequently, the plunger head 4 reaches the plunger abuttingportion 23, and thus the plunger 4 is stopped in the opening position,shown in FIG. 5.

When flow continuity within the piston cooling jet 1 has beenestablished, i.e. when the space between the plunger 4 and the coolantduct inlet 21 is filled, the coolant 5 has reached a value of pressureP2. Subsequently, flow of coolant 5 is slowly increased proportionallyto the increase of pressure above value P2, so that the flow of coolantis nearly constant when the values of pressure of the coolant exceedpressure value P2.

As mentioned, the stroke of the plunger is short and reduced space isformed between the plunger head 4 a and the coolant duct inlet 21. As aresult, short time is needed to fill the space between the plunger 4 andthe coolant duct inlet 21, so that pressure of the coolant reaches avalue of pressure P2 that is slightly different from pressure value P1.As a result, a substantially step like behavior (similar to the idealstep-like behavior of FIG. 8) can be achieved by the piston cooling jet1 according to embodiments of the present disclosure.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing an exemplary embodiment, it being understood that variouschanges may be made in the function and arrangement of elementsdescribed in an exemplary embodiment without departing from the scope ofthe invention as set forth in the appended claims and their legalequivalents.

1-11. (canceled)
 12. A piston cooling jet for an internal combustionengine comprising: a body having a coolant duct extending between acoolant duct inlet and a coolant duct outlet and fluidly connected to acoolant nozzle; a plunger including a plunger stem, a plunger head andat least one plunger coolant channel having a channel inlet at theplunger head and a channel outlet at the plunger stem; and a biasingspring arranged within the coolant duct and biasing the plunger towardsthe closing position; wherein the plunger is configured to move withinthe coolant duct between a closing position wherein the plunger headcloses the coolant duct inlet and an opening position wherein theplunger head spaced from the coolant duct inlet to open the coolant ductfor channeling coolant downstream of the plunger head.
 13. The pistoncooling jet according to claim 12, wherein at least part of the plungercoolant channel comprises a recess provided in at least one of theplunger stem or the plunger head.
 14. The piston cooling jet accordingto claim 13, wherein at least one of the plunger stem or the plungerhead comprising a cross-shaped cross section with respect to a plungerlongitudinal axis.
 15. The piston cooling jet according to claim 12,wherein at least part of the plunger coolant channel comprises a ductprovided within at least one of said plunger stem or said plunger head.16. The piston cooling jet according to claim 12, wherein said biasingspring comprising a coil spring coupled to at least a portion of alateral surface of the plunger steam, wherein at least part of theplunger coolant channel extends within an inner hollow space of the coilspring.
 17. The piston cooling jet according to claim 12, wherein theplunger comprising a plurality of plunger coolant channels.
 18. Thepiston cooling jet according to claim 12, wherein a portion of theplunger coolant channel at the plunger head is arranged substantiallyperpendicular with respect to a plunger longitudinal axis.
 19. Thepiston cooling jet according to claim 12, wherein a portion of theplunger coolant channel at the plunger head is inclined with respect toa plunger longitudinal axis.
 20. The piston cooling jet according toclaim 12, wherein a portion of the plunger coolant channel at theplunger steam is arranged substantially parallel with respect to aplunger longitudinal axis.
 21. The piston cooling jet according to claim12, wherein the plunger head is dimensioned so that, in the openingposition, the plunger is distanced from the coolant duct inlet by adistance that is less than a height of the plunger head.
 22. The pistoncooling jet according to claim 12, wherein the coolant duct comprises aplunger abutting portion, the plunger head contacting said plungerabutting portion in said opening position.
 23. An internal combustionengine comprising: an engine block defining a cylinder; a reciprocatingpiston disposed in the cylinder and coupled to a crankshaft; a cylinderhead closing the cylinder to define a combustion chamber; and a pistoncooling jet including a body having a coolant duct extending between acoolant duct inlet and a coolant duct outlet and fluidly connected to acoolant nozzle, a plunger including a plunger stem, a plunger head andat least one plunger coolant channel having a channel inlet at theplunger head and a channel outlet at the plunger stem, and a biasingspring arranged within the coolant duct and biasing the plunger towardsthe closing position; wherein the plunger is configured to move withinthe coolant duct between a closing position wherein the plunger headcloses the coolant duct inlet and an opening position wherein theplunger head spaced from the coolant duct inlet to open the coolant ductfor channeling coolant downstream of the plunger head, through thecoolant nozzle towards an underside of the pistons in the cylinder ofthe engine block.